Pitch and pitch products have been around since biblical times. Noah made wood tar pitch which is a thermal polymerization product of tree sap, heated for a long time to induce the polymerization.
Coal tar pitch is one of the end products of destructive distillation of coal. Subjecting coal to high temperatures causes vaporous products to separate out of the coal sample. These vaporous products, when fractionated to remove light ends, produce coal tar pitch, which is a glassy solid at room temperature.
Another pitch product is produced from petroleum (crude oil). The most common processes used to generate petroleum pitches are, singularly or a combination of, (a) solvent deasphalting, (b) oxidation, (c) catalytic, and (d) thermal processes. Feedstocks to produce petroleum pitch can be comprise of compositions that range from predominantly aliphatic to predominantly aromatic type chemical structures, as disclosed in Developing Coal Tar/Petroleum Pitches, R. H. Wombles, M. D. Kiser, “Developing Coal Tar/Petroleum Pitches”, Light Metals, 2000, The Minerals, Metals, and Materials Society, Warrendale, Pa. 2000.
Each of these types of “pitch” generally have specific and unique characteristics that make each type of pitch useful for producing different types of intermediate and/or end products. For example, coal tar pitch is suitable for many uses, including but not limited to roofing material, a binder for anodes, a binder for clay pigeons, and myriad other uses. The primary disadvantage or concern with coal tar pitch is the high level of polycyclic aromatic hydrocarbons, some of which are regulated by governmental agencies (OSHA regulations (1910.1200)) present in the processing of the coal tar pitch and in the resulting end products.
The McHenry U.S. Pat. No. 5,746,906 described reducing the level of irritating and/or regulated polycyclic aromatic hydrocarbons in a pitch product by blending a high softening point coal tar pitch with a lower softening point petroleum pitch product. The combined pitch product had a much lower polycyclic aromatic hydrocarbon content, some of which are regulated by governmental agencies (OSHA regulations (1910.1200)) by replacing some of the coal tar derived compounds with those of petroleum origin.
The Nash U.S. Pat. No. 2,768,119 describes pitches made from petroleum which have properties similar to coal tar pitches.
There have been other attempts at reducing the amount of coal tar pitch used in products in some low softening point applications. A series of driveway sealer patents have recently issued relating to blends of coal tar pitch and petroleum pitch, and blends of petroleum pitch with conventional asphalts produced in a refinery, including U.S. Pat. No. 6,267,809, Boyer et al. These materials have satisfactory performance as a sealer base and as coatings.
The pitch products discussed above can be generally classified as high tech, high softening point pitch (for binder pitch application) or as low-tech, low softening point pitch (for driveway sealers and coatings). In the high tech, high softening point applications, the pitch is subjected to many stringent processing requirements and there are strict limits on the amounts sulfur and other impurities that can be present. In the low softening point, lower tech, applications, the product specifications generally permit much higher levels of sulfur and other impurities.
A typical example of one pitch application is as a binder for clay pigeons or other porous materials. Most clay pigeons are currently made from a mixture of pulverized limestone and a commercially available coal tar pitch. In this application the glassy nature, or crystalline behavior, of the coal tar pitch is a highly desirably property. The crystalline behavior causes the clay pigeon, when struck by a shot, to disintegrate. However, the clay pigeon must also possess significant strength so that the clay pigeon can be launched by hand or mechanical launcher without disintegrating during launch. Another example is a related, and somewhat heavier, clay pigeon designed to roll along the ground and simulate a rabbit or other small forest creature. Other types of targets with varying dominions are also produced to provide different challenges to shooting sports. Examples of these target types include the “Midi”, “Mini”, “Battue” and “Flash”. Black's 1998 Wing & Clay, L. Re editor, JFB, Inc., Red Bank, N.J., pg. 222.
The Hukkanen U.S. Pat. No. 4,382,054 describes a pitch made of gypsum containing crystal water and other ingredients such as high water binding substitutes such as calk (CaO).
The Brander et al. U.S. Pat. No. 5,649,707 describes a calcium based clay pigeon with calcium and limestone or mortar having a coal tar pitch petroleum resin as a binder.
While clay pigeons manufactured with pitch as a binder have been sold and used for over a century, one drawback to this well proven commercial product is that there is growing concern about the toxicity of the clay pigeon residue. OSHA regulations (1910.1200) require reporting on the Material Safety Data Sheet (MSDS) of certain compounds if the concentration is equal to or greater than 0.1 wt %. Further details may be found at their Web site, http://www.osha-sic.gov/OshStd_data/1910.1200.html United States Department of Labor, Occupational Health & Safety Administration, Mar. 7, 2002.
While the amounts of compounds such as those described above are relatively small, there are still some concerns about spreading an arguably toxic or hazardous substance on the land. Therefore, there is a growing demand for a clay pigeon which performs satisfactorily, but which has less environmental impact.
In particular, a significant concern exists over specific polycyclic aromatic hydrocarbons being carried into the water table by the United States Environmental Protection Agency. Details of these concerns may be found in the USEPA Web site, http://epa.gov/ttn/atw/hlthef/polycycl.html, United States Environmental Protection Agency, Mar. 7, 2002.
In recent years, there have been many attempts to produce a pitch-free clay pigeon product, and even produce one that was edible, but so far only one, using sulfur as a binder, has received any significant acceptance in the market place. These products typically require elaborate processing steps, so that while a biodegradable, even edible, target can be made, it is expensive and the resulting target has not met with wide spread acceptance.
The Allison et al. U.S. Pat. No. 2,831,778 describes a target made of 60-66% limestone, and 30-35% coal tar pitch, and 1-5% of paraffinic oil such as “residual oil # 6”.
The Rutledge U.S. Pat. No. 2,211,244 describes a target containing 65% wt. coal tar pitch and 35% wt. limestone dust.
The Sato U.S. Pat. No. 4,921,417 describes clay pigeons made of soil, ice and asphalt, which is painted before being cooled to prevent an oil element oozing from the inside of asphalt clay pigeon.
The Goodson U.S. Pat. No. 5,174,581 describes a biodegradable and edible clay pigeon composed of sugar, birdseed, and water.
The Moore U.S. Pat. No. 5,389,142 describes a biodegradable clay target of clay, water, and a sodium silicate/sugar binder.
The Maryska U.S. Pat. No. 5,397,132 describes a gypsum based clay pigeon having a thin, and relatively brittle, skin over softer particulate gypsum composition on the inner body.
The Hellings U.S. Pat. No. 5,467,998 describes a non-toxic, edible, skeet made of flour, water, and ground seeds.
The LaVorna et al. U.S. Pat. No. 5,651,550 describes a biodegradable, edible target of ground forage.
The Lynn Jr., et al. U.S. Pat. No. 5,676,377 describes a biodigestable cold-skeet target comprised of finely ground food grains or seeds in a molasses binder.
The Harshaw et al. U.S. Pat. No. 5,788,243 describes a biodegradable target comprising cellulose wood flour, an organic binder, and a release agent.
The Wisocki et al. U.S. Pat. No. 5,915,695 describes a biodegradable target made from a mixture of clay material and peat material molded into a shape of a target.
The Skeus et al. U.S. Pat. No. 5,947,475 describes an environmentally safe target made from sulfur and fillers such as gypsum, sand, clay, fly ash, glass, metallic sulfate, non-metallic sulfates, rock, mexaloxides and silicates. The patent also describes a prior art as a brand of targets called “White Flyer” (target made of petroleum pitch and limestone). This patent reported that international publication number WO 94/09339 taught use of sulfur and chalk as fillers, and that Canadian Patent 959203 and German Patent 22 54 725 described pitch free targets.
The Gase et al. U.S. Pat. No. 6,257,582 B1 describes a method of making a target by mixing gypsum, grain flour, water and liquid to form a pastry mix and extruding it and drying it to form a target.
The Schreiner-Hansen U.S. Pat. No. 4,271,118 describes a non-toxic clay pigeon of plaster, calcium carbonate, and surfactants.
Neat petroleum pitch, such as Marathon Ashland Petroleum A-240 pitch or Troulmen T-250 pitch, has been used for many years for the production of clay pigeons. Like coal tar pitch, petroleum pitch has been successfully used to product clay pigeon targets. However, similar concerns have arisen as with coal tar pitch since petroleum pitch also contains as polycyclic aromatic hydrocarbons, some of which are regulated by governmental agencies (OSHA regulations (1910.1200)). Concentrations of these compounds are significantly lower in petroleum pitch than in typical coal tar pitches, however some are still above the limits considered to be reportable per OSHA regulations (1910.1200). Other, non-regulated polycyclic aromatic hydrocarbon have also been detected in petroleum pitch.
In addition to the manufacturing costs, there are other concerns with some of the “green” clay pigeons, either with susceptibility to water damage in storage, instability in storage, or deposition of an unpleasant (although environmentally benign) looking residue on the ground.
Therefore, there is a continuing need for an improved pitch product with reduced polycyclic aromatic hydrocarbon content.
There is a further need for a binder useful to produce a rapidly-solidifying frangible pitch.
There is still a further need to produce improved products with such binder, including, for example, clay pigeons.